1. Field of the Invention
The present invention relates to emergency gas and electricity shutoff equipment and control systems therefor. In particular, the present invention relates to the shutoff of the flow of natural gas to a home or other point of use for reasons of safety during emergencies such as seismic events, fires, etc. The present invention further relates to apparatus and systems for shutting off the electricity at a home or other point of use under similar conditions.
2. State of the Prior Art
Various devices have been known in art for shutting off gas systems in the event of a seismic disturbance or the like. For example, U.S. Pat. No. 4,311,171 to Nobi requires a first ball to close a fuel line and at least a second ball, wherein the second ball is mounted within the casing so that a tremor would cause the second ball to dislodge the first ball from its pedestal. The ball for closing the fuel line is required to be mounted in a concave cup supported by a plurality of ball bearings, and includes a concave member as well as a resilient means such as a spring for biasing the cup against the concave member.
U.S. Pat. No. 4,565,208 to Ritchie requires the inclusion of a track and at least a ball riding in the track, and in addition requires the inclusion of “an obstruction” which causes the ball to leave the track when a seismic disturbance causes the ball to contact the obstruction with sufficient energy. It further requires the obstruction to include an incline surface that extends over the track and has a height which decreases across the width of the track.
U.S. Pat. No. 4,475,565 to Keller et al. discloses a magnetically actuable shock responsive unit. This unit includes a valve mechanism for shutting off the flow in a fluid line and is operable upon shock induced horizontal displacement of a weight relative to a support to actuate the valve. An electromagnet is provided for providing a separate actuation of the weight. Movement of the weight from its support to the side of the housing causes the weight to engage a movable tube that releases a mechanism that closes the valve.
U.S. Pat. No. 4,903,720 to McGill, one inventor of the present invention, discloses a safety shutoff device usable in any position. An inertia ball engages a first member so as to move the first member from a first position to a second position in response to vibrations or shocks imparted to the housing.
U.S. Pat. No. 5,119,841 discloses another safety shutoff apparatus using an inertia ball that normally rests on an indented surface. A lever is pivotally mounted with a permanent magnet mounted beneath the free end of the lever. When a shock or vibration causes the inertia ball to jump onto the lever and roll toward its free end, the inertia ball is attracted to the permanent magnet so as to cause the lever to be pivoted downwardly.
Further seismic safety valves are described in U.S. Pat. Nos. 5,409,031, 4,903,720 and 5,119,841.